Explosive composition and method for producing the same

ABSTRACT

An explosive composition in which the explosive reactive component is adsorbed and held on the surfaces of and between the organic hollow microspheres, and a method of producing the same.

TECHNICAL FIELD

The present invention relates to an explosive for industrial use. Moreparticularly, it relates to an explosive composition that can be usedfor various destructive works such as blasting, crushing, excavation,etc., in the field of civil engineering and construction, miningoperations such as quarrying, coal and other ore mining, etc., andoperations in agricultural and forestry industries including drainage,irrigation, grubbing and lumbering.

BACKGROUND ART

Slurry explosives and emulsion explosives are typical of theconventional hydrous explosives. In these explosives, the activeexplosive components comprising an oxidizer solution, an inflammablematerial and a sensitizer and the bubbles are held stably in highconcentrations in a mass in the presence of a sizing agent, and theseexplosives are usually detonated by means of a detonator. In the slurryexplosives, the aerated bubbles or chemical bubbles are usually allowedto exist in the explosive composition to let them play a role like asensitizer, and guar gum is used as sizing agent to compose an aqueousgel. In the emulsion explosives, an oxidizer solution and an oil servingas an inflammable agent are combined to form a W/O type emulsion in thepresence of a surfactant serving as a sizing agent. The bubbles in theseexplosives comprise glass or resinous microballoons, besides the aeratedbubbles.

Use of hollow monocellular thermoplastic particles for the improvementof detonation or the adjustment of density of these explosives ismentioned in U.S. Pat. No. 3,773,573 and JP-A-54-92614 with reference toslurry explosives and in JP-A-56-100192 and JP-A-59-78994 with referenceto emulsion explosives. In U.S. Pat. No. 3,773,573 is disclosed atechnique for application of hollow monocellular thermoplastic particlesto a wide variety of explosives including slurry explosives, accordingto which the explosive composition is heated to a temperaturesubstantially equal to the foaming temperature of the thermoplasticparticles in the presence of the unfoamed resin particles in theproducing process of the explosive charge. However, since heating wasusually unrequired in the manufacture of slurry explosives, resinfoaming in the producing process had little practical significance.Further, even if foaming by heating in the producing process wasnecessary, as understood from the explanation in JP-A-54-92614, therehas been no alternative but to employ a two-stage system in which, forthe reason of safety, a sensitizer is mixed after foaming by heating atthe stage not yet added with the sensitizer has been completed.

In these hydrous explosives, delicate adjustment of the explosivecomponents and the gel or emulsion structure is necessary formaintaining the detonation performance without containing a highlysensitive agent like nitroglycerin in dynamite, and a high-leveltechnique is required for such adjustment. Thus, in the manufacture ofsaid hydrous explosives, since the explosive detonation was affected bythe quality and behavior of the explosive components through the formingprocess of the structure, a great deal of time and labor have beenrequired for the control of quality of the starting materials and/or thecontrol of the explosive producing conditions. As a result, there wouldarise the serious problems such as frequent production of the explosivesof poor quality, which are unable to endure storage, and excessivedeterioration of detonation performance with time. Especially when theamount of the chemical foams or the foaming agent used for theadjustment of density of the explosive composition is increased, it notonly becomes harder to obtain the intended initial performance of theexplosive but also the problem of deterioration of detonationperformance with time becomes even more serious.

Further, the slurry explosives have their peculiar gel elasticity andlack plasticity, and when they are packed into a cartridge, such acartridge itself proves to be soft and limp, so that it is hard tohandle and also difficulties are encountered in inserting the cartridgeinto a blast hole, resulting in a reduced working efficiency forblasting operation. Also, because of poor moldability of this type ofexplosives, it was hard to use the explosives in the bare form withoutcartridge.

In the case of emulsion explosives, when they are given a suddenpressure, the emulsion structure could be destroyed to lose theirdetonating function (this phenomenon is called dead pressingphenomenon), and in short-delay blasting which is a normal form ofblasting operation, there would be left an unexploded residue, posing adifficult problem for disposal thereof.

DESCRIPTION OF THE INVENTION

An object of the present invention is to provide an explosivecomposition which is basically composed of an oxidizer, water andorganic hollow microspheres and which has a highly stabilized burstingperformance and long-time keeping quality without a gel or emulsionstructure such as seen in the conventional hydrous explosives.

Another object of the present invention is to provide an explosivecomposition which can be handled with safety, produces few unexplosedresidue after blasting and is also capable of reducing the degree ofharmfulness of the produced gases.

Still another object of the present invention is to provide alow-detonation-rate explosive having a stabilized blasting performanceeven in the low-density section, which has been difficult to obtain withthe conventional explosives.

The ardent researches by the present inventors for overcoming the aboveproblems of the conventional hydrous explosives have led to theattainment of the present invention.

Thus, the present invention provides a novel explosive compositioncharacterized in that a liquid phase mainly composed of an oxidizer andwater and containing substantially no viscous component is adsorbed andheld on the surfaces of and/or between the organic hollow microsphereswhich are an inflammable component.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a microphotograph showing a fragmental fine structure of theexplosive composition according to the present invention.

FIG. 2(a) is a schematic illustration of the above structure, and 2(b)and 2(c) are schematic illustrations of the conventional powdercompositions.

BEST MODE FOR CARRYING OUT THE INVENTION

The fine structure of the explosive composition according to the presentinvention can be confirmed from, for example, microphotographs. As seenfrom FIG. 1 which is a typical microphotographical representation of thestructure of the present explosive composition, the composition is anaggregation of small granular bodies each comprising an organic hollowmicrosphere 2 having a high-concentration oxidizer solution 1 adheringto its periphery. A conceptual illustration of this structure is givenin FIG. 2(a), from which it is seen that in the explosive composition ofthis invention the organic hollow microspheres 2 constitute thestructural core of the composition. This is a contrast to thecompositional structure of the conventional slurry explosives in which,as shown in FIG. 2(b), the aerated bubbles 5 and hollow bodies 4 aredispersed in a gelled oxidizer/sensitizer phase 3. In the emulsionexplosives, as shown in FIG. 2(c), the hollow bodies 4 such as glassmicroballoons are dispersed in an emulsified oxidizer solution phase 6.It is thus obvious that the explosive composition of the presentinvention is quite different from those of the conventional slurry andemulsion explosives in form of bubbles, form of the oxidizer solutionand structure of the composition. More specifically, the composition ofthis invention requires no gelling agent needed in the conventionalslurry explosives and has a structure in which, unlike the conventionalslurry explosives, the bubbles are incorporated in a stable form in theorganic hollow microspheres which are an inflammable component. Also, ascompared with the emulsion explosives, the composition of this inventionrequires no oil phase as an inflammable component, no surfactant forforming an emulsion and no glass microballoons for holding the bubbles,which presents a striking contrast to the conventional emulsionexplosives.

It has been known to use the hollow monocellular thermoplastic particlesin the conventional slurry explosives, but the amount of such foams hasbeen practically limited to about 2% at most in view of storagestability and blasting performance of the explosive composition. In thepresent invention, it was found quite surprisingly that by increasingthe ratio of the organic hollow microspheres in a compositionsubstantially consisting of an oxidizer solution and said microspheres,it is possible to obtain an explosive composition having a stabledetonation performance even if no gelling agent, wax or surfactant isused. Further, since said hollow microspheres can concurrently serve asan inflammable component, it has become possible to provide an explosivewith excellent performance without necessarily requiring use of aninflammable agent such as carbon or aluminum powder and a sensitizermainly composed of an organic nitrate and/or an inorganic nitrate.

It is quite remarkable that in the explosive composition of the presentinvention, there takes place no separation of the liquid phaseconstituting principally the oxidizer component nor visually noticeablecrystal separation of the oxidizer, and a stable structure can bemaintained, so that the composition of this invention can be applied toa variety of explosives ranging from detonator explosives to boosterexplosives. Especially when the average thickness of the explosivecompound layer around the organic hollow microsphere becomes about 20 μmor less as observed by a microscope, it is noted that the composition iseven more stabilized.

The oxidizer used in the present invention can be selected from thoseknown in the art. Examples of such oxidizers include ammonium salts,alkali metal salts and alkaline earth metal salts of inorganic acidssuch as nitric acid, chloric acid, perchloric acid and the like, andthese oxidizers can be used either singly or in combination. Among theseoxidizers, ammonium nitrate is especially recommendable as it has highsolubility in water and is also easily available. The content of theoxidizer in the composition of the present invention is decidedaccording to the specifications of the explosive to be produced, butusually it is in the range of 50 to 90% by weight based on the wholecomposition. When this oxidizer content is below the above-definedrange, the quantity balance between oxygen and inflammable component istipped to the minus side for oxygen, resulting in an increased toxicityof the gases released after blasting. On the other hand, when saidcontent exceeds the above range, the blasting reactivity lowers toimpair detonation propagation.

The water content in the composition of this invention is usually in therange of 3 to 20% by weight based on the whole composition. When thewater content is below this range, the solid content of the explosivecomposition increases to affect the stable blasting performance thereof,while a too high water content results in a reduced detonatingperformance.

The organic hollow microspheres used in the present invention arepreferably those made by using an organic high-molecular weight compoundas base material. Examples of the organic high-molecular weightcompounds usable here include phenol resins, epoxy resins, urea resins,unsaturated polyester resins, polyimides, maleic acid resins, melamineresins, celluloses, vinyl chloride, vinylidene chloride, acrylonitrile,acrylic acids, acrylic acid salts, acrylic esters, methacrylic acids,methacrylic acid salts, methacrylic esters, single polymers orcopolymers of styrene, ethylene, propylene, butadiene, vinyl acetate andthe like, polycarbonates, polysulfone, polyacetal, polyamides,polyethylene oxide, polyphenylene oxide and the like. These compoundsmay be used either singly or in combination. Among these organichigh-molecular weight compounds, those having thermoplasticity, such asvinylidene chloride-acrylonitrile copolymer, vinylidenechloride-acrylonitrile-methacrylic ester copolymer,acrylonitrile-acrylic ester copolymer and the like are especiallypreferred for use in carrying out the process of the present invention.It is to be noted that the unfoamed microparticles of a vinylidenechloride-acrylonitrile copolymer or methyl methacrylate-acrylonitrilecopolymer incorporated with a low-boiling point hydrocarbon can beeasily made into hollow microspheres by heating, so that they can beused in a heat-foamed form after mixed with the explosive composition.

The organic hollow microspheres used in the composition of the presentinvention are not specifically defined; they may be hollow spherescontaining a gas or air in the inside hollow portion or hollow bodieshaving closed or open spaces therein, but hollow spherical bodies arepreferred for efficiently forming the hot spots where the explosivecharge is detonated. The gas held in the organic hollow spheres may beair, a low-boiling point hydrocarbon, other inflammable gas, or amixture thereof. The recommendable particle size of the organic hollowmicrospheres is about 1,000 μm or less in diameter. When the particlesize exceeds this limit, the hot spots for initiating explosion arereduced in number, making it difficult to produce good detonationproperty. More preferably the organic hollow microspheres have aparticle diameter of 20 to 200 μm as these spheres can provide astabilized explosion without lowering the velocity of detonation. Thefilm thickness of the organic hollow microspheres is not critical; itmay be properly selected as far as the film has enough strength to givea space for accommodating the explosive composition. Usually, the filmthickness is 0.1 to 5 μm. In case the organic high-molecular weightcompound forming the organic hollow microspheres is the thermoplastictype, there are used those microspheres whose film thickness in thefoamed state is about 0.1 to 2 μm since they are required to be capableof being foamed by heating in the explosive composition. The organichollow microspheres in the explosive composition of this invention areusually of a bulk density of about 0.01 to 0.3 as measured in a drystate. The amount of the organic hollow microspheres in the compositionis usually about 2 to 15% by weight based on the whole composition. Thedensity of the explosive composition can be controlled by the amount ofthe organic hollow microspheres. Generally, when the ratio of theorganic hollow microspheres in the composition is too low, thedetonating efficiency is lowered, and it also becomes difficult tomaintain a stabilized blasting performance for a long time. On the otherhand, when the ratio of said organic hollow microspheres is too high,the power of explosion is lowered to jeopardize the blastingreliability.

According to the present invention, it is possible to obtain anexplosive composition having a density ranging from 0.2 to 1.4 g/cm³ ina stabilized way be adjusting the extent of foaming of the organichollow microspheres. The explosive composition of this invention has avelocity of detonation of usually about 1,500 to 5,500 m/sec.

In a process for preparing the explosive composition of this invention,a mixture of an oxidizer and water is heated to a degree that will causesubstantial dissolution of the mixture, and then the organic hollowmicrospheres are uniformly mixed therein.

The method for heat-foaming the organic microspheres is not specified inthis invention, but the following methods may be cited as recommendableexamples: 1 an oxidizer, water and the foamable organic microspheres areheated to a temperature that allows substantially uniform mixing of saidmaterials to form a mixed solution, and then this solution is dropped orsprayed onto a heated plate or into an atmosphere adjusted to atemperature, or above that, at which said microspheres are caused tobegin foaming, thereby foaming the organic microspheres contained insaid mixed solution; 2 an oxidizer, water and the foamable organicmicrospheres are heated to a temperature allowing substantially uniformmixing of said materials to form a mixed solution, and the solution issupplied into a metal tube heated to a temperature, or above that, whichcauses start of foaming of said microspheres, thereby foaming theorganic microspheres contained in said mixed solution; 3 a mixedsolution of an oxidizer, water and the foamable organic microspheres isput into a container and this container is heated in an external bath ofa temperature at which foaming of said microspheres takes place, therebyfoaming the organic microspheres contained in said mixed solution; 4 anoxidizer, water and the foamable organic microspheres are uniformlymixed and heated to a temperature that allows substantially uniformmixing of said materials to form a mixed solution, then an amount ofthis solution determined by taking into consideration the volumeexpansion thereof (on heating) was filled in a heat-resistant film tube,and after deairing and hermetically closing said film tube, it wasplaced in a hot bath or oil bath heated to a temperature, or above that,at which foaming of said microspheres begins, thereby foaming theorganic microspheres contained in said mixed solution; 5 a mixture of anoxidizer and water is heated to cause dissolution of the best part ofthe solid salts to form a high-concentration salt solution, then thissolution is heated to a temperature, or above that, at which foaming ofthe foamable organic microspheres takes place, and said organicmicrospheres are mixed in said solution. In these methods, in case it isexpected that water will be evaporated from the composition, the amountof water that may be evaporated is estimated and water is added in anexcess amount so that the desired explosive composition will beprovided. Also, according to the process for producing the explosivecomposition of this invention, it is possible to optionally change thefoaming condition by adjusting the temperature, and there can beobtained a variety of explosives ranging from the type detonated by abooster to the type that can be detonated by a single percussion. Theunfoamed organic microspheres are increased in internal pressure byheating and begin to foam as they are heated close to a temperature atwhich the organic polymer film begins to soften, and they are expandedabout 20- to 100-fold in volume ratio. However, if the organic hollowmicrospheres are heated more than necessary and bursted, they can nolonger serve as an effective component of an explosive, so that it isrecommended to stop heating before reaching a temperature at whichoverfoaming may be caused.

The explosive composition according to the present invention can bepresented in various forms such as solid, powder, flakes, paste, etc.,and it can be packed with a known packaging material such as paper,laminated paper, plastic film, laminated plastic film, paper tube,plastic tube, etc., selected according to the form of the composition,its properties, object of use and other factors, and thus can becommercially offered in the form of packs.

The explosive composition of this invention is capable of wellsatisfying the quality requirements for an explosive, but for additionalimprovement of blasting performance, an organic nitrate such as a lowersaturated aliphatic amine or an inorganic nitrate such as hydrazinenitrate may be added as a sensitizer to accommodate use in the colddistricts. Also, in consideration of gas release after blasting in atunnel or underground mine, a solid inflammable material such as coalpowder or aluminum powder may be additionally supplied. Other pertinentsubstances, for example, an activator such as phosphoric ester, adecomposition inhibitor such as urea, etc., may be safely added asdesired.

With the explosive composition and its producing method according to thepresent invention, there can be obtained a variety of explosives rangingfrom the booster-blasted type to the percussion-initiated type, and theexplosives with a wide variety of dead pressing density. The presentinvention can be applied to formulation of almost all sorts ofconventional explosives. Also, the explosive composition of thisinvention is improved in dead pressing phenomenon attendant on theemulsion explosives, that is, improved in anti-dead pressing property,and the safety in the work field can be further improved due to thereduction of the unexploded compound residue. The production methodaccording to this invention needs no high-degree production techniquessuch as required in the production of the conventional slurry andemulsion explosives, and is capable of producing a desired type ofexplosive with ease and safety.

The explosive composition of this invention can be usually detonated byusing various known systems such as electric detonator, industrialdetonator, detonator with blasting tube, detonator with gas-blastingtube, electromagnetic detonator, laser detonator, wireless detonator,blasting fuse, detonating fuse, etc. In some cases, the explosivecomposition may be detonated by using a booster.

EXAMPLES

The present invention will hereinafter be described in more detail withreference to the examples thereof, which examples, however, are merelyintended to be illustrative and not to be construed as limiting thescope of the invention. The cap sensitivity, booster performance,velocity of detonation, cartridge propagation in steel tube andanti-dead pressing property in sand were determined by the followingmethods.

Determination of cap sensitivity

An explosive charge was densely packed in a polyethylene laminated papertube or a nylon 66 film tube (pack diameter: 20 mm or 30 mm; packlength: about 200 mm) and kept in a refrigerator of about -30° C. forabout 15 hours. Thereafter, the charge, with its temperature adjusted,was detonated by a #6 detonator, and the temperature at which the chargewas perfectly exploded was measured. For evaluating the keeping quality,the same detonation test was conducted on the same explosive chargewhich has been kept in storage for one year after production thereof.

Determination of booster performance

A test explosive filled in a steel cylinder (JIS G 3452 32A; innerdiameter: 36 mm; length: 350 mm) closed on one side in the longitudinaldirection was detonated by a booster (50 g of #2 Enoki dynamite attachedwith a #6 detonator), and from visual observation of the state ofwrecking of the steel cylinder, it was determined whether perfectexplosion occurred or not. For evaluating the keeping quality, the samedetonation test was conducted on the same explosive which has been keptin storage for one year after production thereof.

Determination of velocity of detonation of packed explosive

An explosive charge packed in a polyethylene laminated paper tube or anylon 66 film tube (pack diameter: 20 mm or 30 mm; pack length: 300 mm)was detonated by a #6 detonator, and the velocity of detonation wasdetermined by the ion gap method. For evaluating the keeping quality,the same detonation test was conducted on the same explosive which hasbeen kept in storage for one year after production thereof.

Determination of velocity of detonation of explosive packed steel tube

An explosive packed in a steel tube (JIS G 3452 32A; inner diameter:about 36 mmφ; length: 350 mm) was detonated by a booster (50 g of #2Enoki dynamite attached with a #6 detonator), and the velocity ofdetonation was determined by the ion gas method. For evaluating thekeeping quality the same detonation test was conducted on the sameexplosive which has been kept in storage for one year after productionthereof.

Propagation test by cartridge in steel tube

An explosive charge was packed in a polyethylene laminated paper tube ora nylon 66 film tube (pack diameter: about 20 mmφ; pack length: 150 mm),and about 20 packs were set in juxtaposition to each other in a steeltube (JIS G 3452 40A; inner diameter: about 41.6 mm; length: 3,000 mm)so that no deformation would take place in the longitudinal direction.Then the pack at an end was detonated by #6 detonator and the length ofthe wrecked portion of the steel tube was measured to determinepropagation performance in steel tube. For evaluating the keepingquality, the same test was conducted on the same packs which have beenkept in storage for one year after production thereof.

Determination of anti-dead pressing in sand

An explosive charge was packed in a polyethylene laminated paper tube ora nylon 66 film tube (pack diameter: 30 mm; pack length: about 150 mm).There were prepared 2 packs, and they were arranged side by side andburied 80 cm deep in sand, with an instantaneous #6 electric detonatorattached to one pack while a 10 ms short-delay electric detonatorattached to the other pack. Both electric detonators were connected inseries and electrified for detonating the explosive. This test wasconducted 5 times repeatedly, and it was checked whether the explosivepack attached with the 10 ms short-delay electric detonator wasperfectly detonated or not to determine anti-dead pressing property insand. For evaluating the keeping quality, the same test was conducted onthe same packs which have been kept in storage for one year afterproduction thereof.

Example 1

805 g of ammonium nitrate and 135 g of water were mixed and heated toabout 90° C. Meanwhile, 60 g of organic hollow microspheres (EXPANCEL®551DE (a vinylidene chloride-acrylonitrile-methacrylic ester copolymer)produced by Expancel AB) was weighed out and put into a polyethylenebag. Then the above mixture was charged into the polyethylene bag.Thereafter, the opening of the bag was closed and the materials in thebag were mixed with stirring for about 10 minutes by applying a force tothe bag sidewise thereof and then cooled with water to obtain anexplosive composition with an explosive density of 0.40 g/cm³. Thisexplosive composition was packed in a steel tube (JIS G 3452 32A; innerdiameter: about 36 mm; length: 350 mm) which had been closed on one sidein the longitudinal direction, and detonated by a booster (50 g of #2Enoki dynamite attached with a #6 detonator). There took place perfectdetonation. When the same test was conducted with the same explosivecomposition kept in storage for one year after production thereof, thesimilar results were obtained.

Example 2

1608 g of ammonium nitrate, 310 g of water and 82 g of non-foamedorganic microspheres (MATSUMOTO MICROSPHERE F-30 which is a vinylidenechloride-acrylonitrile-methacrylic ester copolymer produced by MatsumotoYushi-Seiyaku Co., Ltd.) were supplied into a metallic container andmixed with stirring in an external bath of about 80° C. to obtain amixture of about 70° C. There was also prepared a metal plate heated toabout 100°-150° C. The above mixture was dropped peacemeal onto thesurface of said metal plate, whereby a granular explosive compositioncould be obtained in a very short time.

This explosive composition was dispensed and packed in the polyethylenelaminated paper tubes of 20 mm and 30 mm in diameter to obtain theexplosive packs each containing 30-40 g of said composition, and theirblasting performance was examined. The density of the 30 mm-diameterpack was 0.35 g/cm³, and this pack could be detonated by a #6 detonatorat -10° C. The rate of detonation at the temperature of 5° C. was 1,900m/s. The 2 mm-diameter pack was loaded in a steel tube having an innerdiameter of 41.6 mm and a length of 3 m and detonated from one endthereof by a #6 detonator. As a result, all of the explosive charge wasperfectly detonated, and the length of the wrecked portion of the steeltube was 3 m. Further, two pieces of said 30 mm-diameter explosive packwere subjected to an in-sand dead pressing test in which the two packswere buried in sand parallel to each other with a spacing of 15 cmtherebetween, with an instantaneous #6 detonator attached to one packand a 10 ms short-delay electric detonator attached to the other pack,and detonated by electrifying said detonators. This test was conducted 5times, and both packs were perfectly detonated in each run of test. Whenthe same test was conducted using the same packs which have been kept instorage for one year after production thereof, the similar result wasobtained. On the other hand, when the same test was carried out usingthe conventional slurry and emulsion explosives prepared by an ordinarymethod, with the charge density properly adjusted, any of the packscould not be detonated by a #6 detonator a temperature below 0° C. Also,in an explosive charge propagation test in a steel tube, detonation wasinterrupted at a point close to 1.2 m from the detonated end, and thelength of the wrecked portion of the steel tube was about 0.8-1.6 m.Further, in an in-sand dead pressing test, two of the explosive packsattached with a 10 ms short-delay electric detonator were not perfectlydetonated and recovered as incompletely exploded packs. When the sametest was conducted with the same packs kept in storage for one yearafter production thereof, it was found that any of them was deterioratedin performance quality to an extent that they could not be detonated bya #6 detonator.

Examples 3-5

The following explosive compositions were produced in the same way asExample 1, and their blasting performance was examined.

    ______________________________________                                                   Example 3                                                                             Example 4   Example 5                                      ______________________________________                                        Ammonium nitrate                                                                           1530   g      1550  g     1530 g                                 Water        270    g      270   g     270  g                                 Non-foamed organic                                                                         200    g      --          --                                     microspheres 1                                                                Non-foamed organic                                                                         --            180   g     --                                     microspheres 2                                                                Non-foamed organic                                                                         --            --          200  g                                 microspheres 3                                                                ______________________________________                                    

The non-foamed organic microspheres 1 were the same as used in Example2. The non-foamed organic microspheres 2 were made of anacrylonitrile-methyl methacrylate copolymer (053WU produced by ExpancelAB), and the non-foamed organic microspheres 3 were composed of anacrylonitrile-acrylic ester copolymer (MATSUMOTO MICROSPHERE F-30,Matsumoto Yusi-Seiyaku Co., Ltd.).

The 20 mm-diameter and 30 mm-diameter pack densities of the above threeexplosive compositions were 0.23, 0.30 and 0.40, respectively. The 30mm-diameter packs at a temperature of -10° C. could be detonated by a #6detonator. The velocity of detonation of said three explosivecompositions at a temperature of 5° C. was 1,900 m/s, 2,000 m/s and2,200 m/s, respectively. When a 20 mm-diameter pack was loaded in asteel tube of 41.6 mm in inner diameter and 3 m in length and detonatedfrom one end thereof, all of the explosive charge was perfectlydetonated and the length of the wrecked portion of the steel tube was 3m. When the same test was conducted using the same explosivecompositions left one year after production thereof, the similar resultswere obtained. On the other hand, when the same test was conducted usingthe conventional slurry and emulsion explosives prepared by an ordinaryprocess, with the explosive charge density being properly adjusted, anyof the explosive packs could not be detonated at a temperature below 0°C. Also, in an explosive pack propagation test in a steel tube,detonation was interrupted at a point close to 0.8-1.6 m from thedetonated end, and the length of the wrecked portion of the steel tubewas about 0.8-1.6 m. The same test was further carried out using thesame explosive compositions kept in storage for one year afterproduction thereof, but any of the compositions has been deteriorated inperformance quality to the extent that it could not be detonated by a #6detonator.

Example 6

1608 g of ammonium nitrate, 310 g of water and 82 g of non-foamedorganic microspheres (MATSUMOTO MICROSPHERE F-30 which is a vinylidenechloride-acrylonitrile-methacrylic ester copolymer, produced byMatsumoto Yusi-Seiyaku Co., Ltd.) were charged into a metallic containerand mixed with stirring in a water bath of about 70° C. to obtain amixture of about 70° C. This mixture was injected into a 20 mm-diametermetallic tube (Teflon coated on the inner wall), which had been heatedto about 100°-150° C., from one end thereof, and an open-cell foamedstring-shaped explosive composition was obtained from the other end.

The thus obtained explosive composition was dispended to form theexplosive packs in the manner described above, and their blastingperformance was examined. The density of the 20 mmφ packs was 0.45g/cm³, and these packs could be detonated by a #6 detonator at atemperature of -5° C. The velocity of detonation at the temperature of5° C. was 1,900 m/s. When an explosive pack, cut to a length of 3 m, wasloaded in a steel tube of 41.6 mm in diameter and 3 m in length anddetonated from one end thereof by a #6 detonator, all of the explosivecharge was perfectly detonated and the length of the wrecked portion ofthe steel tube was 3 m. Further, two pieces of said 30 mmφ explosivepack were subjected to an in-sand dead pressing test in which the twopacks were buried 80 cm deep in sand parallel to each other with aspacing of 15 cm therebetween, with an instantaneous #6 detonatorattached to one of said packs and a 10 ms short-delay electric detonatorattached to the other pack, and both detonators were electrifiedsimultaneously to cause detonation. This test was conducted 5 times.Both packs were perfectly detonated in each run of test. When the sametest was carried out using the same explosive composition which had beenkept in storage for one year after production thereof, the similarresult was obtained.

Example 7

1,524 g of ammonium nitrate, 286 g of water and 190 g of non-foamedorganic microspheres (MATSUMOTO MICROSPHERE F-30, a vinylidenechloride-acrylonitrile-methacrylic ester copolymer produced by MatsumotoYusi-Seiyaku Co., Ltd.) were put into a metallic container and mixedwith stirring in an external bath of about 90° C. to obtain a mixture ofabout 70°-80° C. This mixture was injected into a 20 mmφ metal tube(Teflon coated on inner wall), which had been heated to about 90°-110°C., from the opening at one end thereof, and a creamy explosivecomposition having a density of 1.35 g/cm³ was obtained from the openingat the other end.

When the above explosive composition was packed in a steel tube (JIS G3452 32A; inner diameter: 36 mm; length: 350 mm), which had been closedon one side in the longitudinal direction, and detonated by a booster(50 g of #2 Enoki dynamite attached with a #6 detonator), saidcomposition was perfectly detonated, and the velocity of detonation was5,460 m/s. When the same test was conducted using the same explosivecomposition kept in storage for one year after production thereof, thesimilar result was obtained.

Examples 8-10

The following explosive compositions were produced by following theprocedure of Example 7, and their blasting performance was examined.

    ______________________________________                                                   Example 8                                                                             Example 9   Example 10                                     ______________________________________                                        Ammonium nitrate                                                                           1560   g      1524  g     1530 g                                 Water        320    g      286   g     270  g                                 Non-foamed organic                                                                         120    g      --          --                                     microspheres 1                                                                Non-foamed organic                                                                         --            190   g     --                                     microspheres 2                                                                Non-foamed organic                                                                         --            --          200  g                                 microspheres 3                                                                ______________________________________                                    

The non-foamed organic microspheres 1 were the same as used in Example1, and the non-foamed organic microspheres 2 were made of anacrylonitrile-methyl methacrylate copolymer (053WU, Expancel AB). Thenon-foamed organic microspheres 3 were composed of anacrylonitrile-acrylic ester copolymer (MATSUMOTO MICROSPHERE F-50,Matsumoto Yusi-Seiyaku Co., Ltd.).

The densities of the above three explosive compositions were 1.38 g/cm³and 1.35 g/cm³, respectively. Each of the above explosive compositionswas packed in a steel tube (JIS G 3452 32A; inner diameter: about 36 mm;length: 350 mm), which had been closed on one side in the longitudinaldirection, and detonated by a booster (50 g of #2 Enoki dynamiteattached with a #6 detonator). As a result, each of said explosivecompositions was detonated perfectly, and the velocity of detonation was5,500 m/s, 4,600 m/s and 5,100 m/s, respectively. When the same test wasconducted on the same explosive compositions which had been kept instorage for one year after production thereof, the similar result wasobtained.

Example 11

1608 g of ammonium nitrate, 310 g of water and 82 g of non-foamedorganic microspheres (MATSUMOTO MICROSPHERE F-30, avinylidene-acrylonitrile-methacrylic ester copolymer, produced byMatsumoto Yusi-Seiyaku Co., Ltd.) were placed in a stainless steelcontainer and heated with slow stirring in an oil bath of about100°-130° C. to obtain a creamy explosive composition. This explosivecomposition was dispensed and packed in the 20 mmφ and 30 mmφpolyethylene laminated paper tubes to form the explosive packs eachcontaining about 50 g of said composition, and their blastingperformance was examined. The density of the 30 mmφ explosive pack was0.70 g/cm³, and this pack could be detonated by a #6 detonator at -5° C.The velocity of detonation at of 5° C. was 2,500 m/s. The 20 mmφ packwas loaded in a steel tube of 41.6 mm in inner diameter and 3 m inlength and detonated from one end by a #6 detonator. All of theexplosive charge was perfectly detonated, and the length of the wreckedportion of the steel tube was 3 m. Further, two 30 mmφ explosive packswere subjected to an in-sand dead pressing test in which said two packswere buried 80 cm deep in sand parallel to each other with a spacing of15 cm therebetween, with a #6 electric detonator attached to one packand a 10 ms short-delay detonator attached to the other pack, anddetonated by electrifying said detonators. This test was conducted 5times. Both packs were perfectly detonated in each run of test. When thesame test was conducted on the same explosive composition kept instorage for one year after production thereof, the similar result wasobtained.

Example 12

1,250 g of ammonium nitrate, 170 g of water and 160 g of sodium nitrate,300 g of monomethylamine nitrate and 120 g of non-foamed organicmicrospheres (MATSUMOTO MICROSPHERE F-30, a vinylidenechloride-acrylonitrile-methacrylic acid copolymer) were mixed whileheating to about 70° C. to form a homogeneous mixed solution. An amountof this solution, determined by taking into consideration possiblevolume expansion on heating, was filled in a 20 mmφ nylon 66 film tube.After deairing this tube and then closing both ends thereof, said tubewas placed in a hot bath of 100°-150° C. to heat the mixed solutiontherein, causing foaming of the organic microspheres contained in saidmixture, and the blasting performance as an explosive composition packedin said nylon 66 film tube was examined. The density of the explosivecharge in said 20 mmφ nylon 66 film tube was 0.35 g/cm³, and thisexplosive pack could be detonated by a #6 detonator at -10° C. Thevelocity of detonation at 5° C. was 2,200 m/s. Also, the above explosivepack was loaded in a steel tube of 41.6 mm in diameter and 3 m long anddetonated from one end thereof by a #6 detonator. As a result, all ofthe explosive charge was perfectly detonated, and the length of thewrecked portion of the steel tube was 3 m. When the same test wasconducted using the same explosive composition which had been kept instorage for one year after production thereof, the similar result wasobtained.

Example 13

1,050 g of ammonium nitrate, 170 g of water, 300 g of sodium nitrate and360 g of monomethylamine nitrate were mixed and heated to about 70° C.to prepare a mixture. Meanwhile, 120 g of organic hollow microspheres(EXPANCEL® 551DE, a vinylidene chloride-acrylonitrile-methacrylic estercopolymer produced by Expancel AB) was weighed out and placed in apolyethylene bag. Then the above mixture was charged into said bag, andafter closing its opening, the bag was subjected to a stirring forceapplied to the bag sidewise thereof for about 10 minutes to mix thematerials in the bag, followed by cooling to obtain an explosivecomposition. This explosive composition was dispensed and packed in the20 mmφ and 30 mmφ polyethylene laminated paper tubes to form theexplosive packs each containing about 30-40 g of said composition, andtheir blasting performance was examined. The density of the 30 mmφexplosive pack was 0.35 g/cm³, and this pack could be detonated by a #6detonator at of -20° C. The velocity of detonation at 5° C. was 2,300m/s. The 20 mmφ explosive pack was loaded in a steel tube of 41.6 mm indiameter and 3 m in length and detonated from one end thereof by a #6detonator. As a result, all of the explosive charge was perfectlydetonated, and the length of the wrecked portion of the steel tube was 3m. Further, a pair of 30 mmφ explosive packs were subjected to anin-sand dead pressing test in which both packs were buried 80 cm deep insand parallel to each other with a spacing of 15 cm therebetween, withan instantaneous #6 detonator attached to one pack and a 10 msshort-delay electric detonator attached to the other pack, and detonatedsimultaneously by electrifying said detonators. This test was conducted5 times, and both packs were perfectly detonated in each run of test.When the same test was carried out using the same explosive compositionwhich had been kept in storage for one year after production thereof,the similar result was obtained.

Examples 14 and 15

The following explosive compositions were produced by following theprocedure of Example 13, and their blasting performance was examined.

    ______________________________________                                                       Example 14                                                                            Example 15                                             ______________________________________                                        Ammonium nitrate 1,520  g      1,330  g                                       Water            80     g      170    g                                       Monomethylamine  350    g      300    g                                       nitrate                                                                       Sodium nitrate   --            160    g                                       Organic hollow   50     g      40     g                                       microspheres                                                                  ______________________________________                                    

The 30 mmφ pack densities of the above two explosive compositions were1.02 and 0.95, respectively, and the packed compositions could bedetonated by a #6 detonator at 0° C. The velocity of detonation at 5° C.was 3,700 m/s and 3,200 m/s, respectively. When the same test wasconducted on the same explosive compositions which had been kept instorage for one year after production thereof, the similar results wereobtained.

Example 16

1,296 g of ammonium nitrate, 164 g of water, 358 g of monomethylaminenitrate and 78 g of non-foamed organic microspheres (MATSUMOTOMICROSPHERE F-30 which is a vinylidenechloride-acrylonitrile-methacrylic ester copolymer produced by MatsumotoYusi-Seiyaku Co., Ltd.) were placed in a metallic container and mixed bystirring the container in a water bath of about 70° C. to obtain amixture of about 70° C. Meanwhile, there was prepared a metal plate(Teflon coated on inner side) heated to about 100°-150° C. The abovemixture was dropped peacemeal onto the surface of said hot metal plate,thereby obtaining a granular explosive composition in a very short time.

This explosive composition was dispended and packed in the 20 mmφ and 30mmφ polyethylene laminated paper tubes to form the explosive packs eachcontaining about 30-40 g of said composition, and their blastingperformance was examined. The density of the 30 mmφ explosive pack was0.80 g/cm³, and this pack could be detonated by a #6 detonator at -15°C. The velocity of detonation at 5° C. was 3,700 m/s. The 20 mmφexplosive pack was loaded in a steel tube of 41.6 mm in inner diameterand 3 m in length and detonated from one end thereof by a #6 detonator.As a result, all of the explosive charge was perfectly detonated, andthe length of the wrecked portion of the steel tube was 3 m. Further, apair of 30 mmφ explosive packs were subjected to an in-sand deadpressing test in which both packs were buried 80 cm deep in sandparallel to each other with a spacing of 15 cm therebetween, with aninstantaneous #6 detonator attached to one pack and a 10 ms short-delayelectric detonator attached to the other pack, and detonatedsimultaneously by electrifying said detonators. This test was repeated 5times, and both packs were perfectly detonated in each run of test. Whenthe same test was conducted on the same explosive compositions which hadbeen kept in storage for one year after production thereof, the similarresults were obtained.

Examples 17-19

The following explosive compositions were produced according to theprocess of Example 16 and their blasting performance was examined.

    ______________________________________                                                   Example 17                                                                            Example 18  Example 19                                     ______________________________________                                        Ammonium nitrate                                                                           1338   g      1490  g     1470 g                                 Water        210    g      170   g     170  g                                 Monomethylamine                                                                            300    g      240   g     240  g                                 nitrate                                                                       Sodium nitrate                                                                             --            140   g     --                                     Non-foamed organic                                                                         152    g      --          --                                     microspheres 1                                                                Non-foamed organic                                                                         --            100   g     --                                     microspheres 2                                                                Non-foamed organic                                                                         --            --          120  g                                 microspheres 3                                                                ______________________________________                                    

The non-foamed organic microspheres 1 are the same as used in Example16, and the non-foamed organic microspheres 2 are made of anacrylonitrile-methyl methacrylate copolymer (053WU, Expancel AB). Thenon-foamed organic microspheres 3 are composed of anacrylonitrile-acrylic ester copolymer (MATSUMOTO MICROSPHERE F-50,Matsumoto Yusi-Seiyaku Co., Ltd.).

The 20 mmφ and 30 mmφ pack densities of the above three explosivecompositions were 0.20, 0.30 and 0.45, respectively. The 30 mmφ pack at-25° C. could be detonated by a #6 detonator. The velocity of detonationat 5° C. was 1,900 m/s, 2,300 m/s and 2,500 m/s, respectively. The 20mmφ pack was loaded in a steel tube of 41.6 mm in diameter and 3 m inlength and detonated from one side by a #6 detonator. The whole packcharged was detonated perfectly, and the length of the wrecked portionof the steel tube was 3 m. When the same test was carried out on thesame explosive compositions which had been kept in storage for one yearafter production thereof, the similar results were obtained.

Example 20

1,346 g of ammonium nitrate, 240 g of water, 80 g of sodium nitrate, 174g of monomethylamine nitrate and 160 g of non-foamed organicmicrospheres (MATSUMOTO MICROSPHERE F-30) were supplied into a stainlesssteel container and heated with slow stirring in an oil bath of about80°-90° C. to obtain an explosive composition with an explosive densityof 1.38 g/cm³. When this explosive composition was charged into a steeltube (JIS G 3452 32A; inner diameter: 36 mm; length: 350 mm), which hadbeen closed on one side in the longitudinal direction, and detonated bya booster (50 g of #2 Enoki dynamite attached with a #6 detonator), theabove explosive composition was perfectly detonated. The velocity ofdetonation was 5,600 m/s. When the same test was conducted on the sameexplosive composition which had been kept in storage for one year afterproduction thereof, the similar result was obtained.

INDUSTRIAL APPLICABILITY

The explosive composition according to the present invention, in virtueof its peculiar structure in which the active component comprising anoxidizer and water or a sensitizer, an oxidizer and water is heldcontinuously on the surfaces of and/or in the spaces between theadjoining microspheres, substantially unnecessitates use of a thickenerwhich has been indispensable for maintenance of quality of theconventional hydrous explosive compositions, and it can not only keepits quality for a long time but also realized practical use of thelow-specific-gravity products which has been considered unfeasible withthe conventional hydrous explosives. Owing to reduction of specificgravity, the noise and vibration generated at the time of blasting canbe remarkably lessened.

We claim:
 1. An explosive composition comprising an oxidizer, water andorganic hollow microspheres, wherein a phase substantially composed ofsaid oxidizer and water is adsorbed and held on the surfaces of and/orbetween said organic hollow microspheres.
 2. An explosive compositionaccording to claim 1, wherein the organic hollow microspheres aresubstantially spherical.
 3. An explosive composition according to claim1 or 2, wherein the organic hollow microspheres are thermoplastic.
 4. Anexplosive composition according to claim 1 or 2, wherein thethermoplastic organic hollow microspheres are made of a vinylidenechloride-acrylonitrile copolymer.
 5. An explosive composition accordingto claim 1 or 2, wherein the thermoplastic organic hollow microspheresare made of a vinylidene chloride-acrylonitrile-methacrylic estercopolymer.
 6. An explosive composition according to claim 1 or 2,wherein the thermoplastic organic hollow microspheres are made of anacrylonitrile-acrylic ester copolymer.
 7. An explosive composition packin which an explosive composition according to claim 1 or 2 is packed ina packaging material.
 8. A method of producing an explosive compositionsubstantially consisting of an oxidizer, water and organic hollowmicrospheres, said organic hollow microspheres being used as aninflammable component, which method comprises mixing 2-15% by weight offoamable organic microspheres, 3-20% by weight of water and the balanceessentially consisting of an oxidizer to prepare a compositionsubstantially free of aerated bubbles, and then heating and foaming saidcomposition.
 9. The method according to claim 8, wherein the foamableorganic microspheres are substantially spherical.
 10. The methodaccording to claim 8 or 9, wherein the foamable organic microspheres arethermoplastic.
 11. The method according to any of claims 8-10, whereinthe thermoplastic foamable organic microspheres are made of a vinylidenechloride-acrylonitrile copolymer.
 12. The method according to any ofclaims 8-10, wherein the thermoplastic foamable organic microspheres aremade of a vinylidene chloride-acrylonitrile-methacrylic ester copolymer.13. The method according to any of claims 8-10, wherein thethermoplastic foamable organic microspheres are made of anacrylonitrile-acrylic ester copolymer.
 14. An explosive composition packin which an explosive composition according to any of claims 8-13 ispacked in a packaging material.
 15. An explosive composition comprisingan oxidizer, water and organic hollow microspheres, wherein a phasesubstantially composed of a sensitizer, an oxidizer and water isadsorbed and held on the surfaces of and/or between said organic hollowmicrospheres.
 16. An explosive composition according to claim 15,wherein the organic hollow microspheres are substantially spherical. 17.An explosive composition according to claim 15 or 16, wherein theorganic hollow microspheres are thermoplastic.
 18. An explosivecomposition according to claim 15 or 16, wherein the thermoplasticorganic hollow microspheres are made of a vinylidenechloride-acrylonitrile copolymer.
 19. An explosive composition accordingto claim 15-16, wherein the thermoplastic organic hollow microspheresare made of a vinylidene chloride-acrylonitrile-methacrylic estercopolymer.
 20. An explosive composition according to claim 15-16,wherein the thermoplastic organic hollow microspheres are made of anacrylonitrile-acrylic ester copolymer.
 21. An explosive composition packin which an explosive composition according to any of claims 15 or 16 ispacked in a packaging material.
 22. A method of producing an explosivecomposition substantially consisting of a sensitizer, an oxidizer, waterand organic hollow microspheres, which comprises mixing 2-15% by weightof foamable organic microspheres, 3-20% by weight of water and thebalance essentially consisting of a sensitizer and an oxidizer toprepare a composition substantially free of aerated bubbles, and heatingand foaming said composition.
 23. The method according to claim 22,wherein the foamable organic microspheres are substantially spherical.24. The method according to claim 22 or 23, wherein the foamable organicmicrospheres are thermoplastic.
 25. The method according to any ofclaims 22-24, wherein the thermoplastic organic microspheres are made ofa vinylidene chloride-acrylonitrile copolymer.
 26. The method accordingto any of claims 22-24, wherein the thermoplastic foamable organicmicrospheres are made of a vinylidene chloride-acrylonitrile-methacrylicester copolymer.
 27. The method according to any of claims 22-24,wherein the thermoplastic foamable organic microspheres are made of anacrylonitrile-acrylic ester copolymer.
 28. An explosive composition packin which an explosive composition produced according to any of themethods of claims 22-27 is packed in a packaging material.